Fish Have Distinct Personalities, Prof Discovers

November 22, 2007 - News Release

Fish have distinct personalities, which explains differences in behaviours like eating and swimming, according to new research by a University of Guelph professor.

In a paper published in the journal Animal Behaviour, Prof. Rob McLaughlin of Guelph's Department of Integrative Biology and researcher Alex Wilson found that fish show extremes for personality traits: staying put or exploring, risk-averse or risk-takers, sociable or aggressive.

"We’ve seen the kinds of phenomena we associate with personality in humans showing up domesticated animals and now in wild animals," McLaughlin said, who teaches, among other things, animal behaviour.

Personality differences can influence more complex behaviours; specifically, he examined the feeding strategies of very young brook trout. McLaughlin and Wilson observed two kinds of feeders among young brook trout in the Credit River near Toronto.

They noted that active feeders swam near the surface, away from the bank. Sit-and-wait feeders remained near the stream bottom, feeding on what passed by. "We wanted to test whether behavioural differences in the field were tied to underlying differences in personality," he said.

So they caught the fish and tested them for six days in the Hagen Aqualab on campus. They found that fish that had been more active in the field spent more time moving in the aquarium, spent less time near the bottom and took less time to emerge from a glass jar than their sedentary counterparts.

Active fish stayed active and changed their activity less, on average, than fish that used a sit-and-wait strategy in the field. Subsequent work by current master's student Michelle Farwell has helped to cancel out potential differences caused by such factors as variations in resting metabolic rates or swimming ability.

"What's cool is the possibility for individual behaviour to influence food webs and interactions between prey and predators, and the evolution of fish populations with groups differing in behaviour and body form," McLaughlin said.

The researchers say their work may help in managing fish stocks more precisely by accounting for personality differences between groups of fish. Setting catch regulations based on studies of fish taken only from the water column, for instance, may cause relatively more active individuals to be caught than sedentary ones, with unexpected consequences for the entire population and for biodiversity.

McLaughlin also suggests that, over many generations, these personality differences along with environmental differences may not only play a role in the creation of subgroups of fish but also the evolution of new species.